1. Field of the Invention
This invention relates to ammonia converters. Specifically, the ammonia converters of this invention are the radial design where the ammonia synthesis gas flows radially through the catalyst beds. Further, the design is full flow, meaning all the synthesis gas feed passes through the first catalyst bed, all the effluent from the first catalyst bed passes through the second catalyst bed and all the effluent from the second catalyst bed passes through the third catalyst bed.
2. Prior Art
U.S. Pat. No. 3,372,988 assigned to Haldor Topsoe discloses an apparatus for ammonia gas synthesis which includes a plurality of annular-shaped, vertically-spaced catalyst beds through which the synthesis gas feed is passed at least in part in a radially outward direction; temperature control of the synthesis gas or catalyst effluent is controlled by the addition of quench gas. The same or an apparatus similar to that of U.S. Pat. No. 3,372,988 is disclosed in the November 1974 issue of Petroleum International, Volume 14, in an article entitled "Radial Converter Shows Big Benefits for Ammonia". A modified version of this converter, which is known as the "Topsoe" converter in the industry, is generally described in the May/June 1976 issue of Nitrogen, in an article entitled "Modified Topsoe Converter Increases Yields". As understood, the modified Topsoe converter utilizes alternating radial flow through each of separate, annular-shaped catalyst beds. An intermediate heat exchanger is utilized in this modified Topsoe converter to heat a secondary quench gas for controlling the temperature of the synthesis gas feed.
The book "Ammonia Part III", edited by A. V. Slack and G. Russell James, published by Marcel Decker, Inc., 1977, also illustrates Topsoe converters on pages 346-347. The Topsoe converter shown on page 346 utilizes radially outward flow; and, the Topsoe converter shown on page 347 utilizes radially outward flow in a first bed and radially inward flow in a second bed. A radial flow ammonia converter designed by Chemoprojekt is illustrated on page 355 of "Ammonia Part III". In the Chemoprojekt unit, a first heat exchanger is positioned radially below an annular-shaped catalyst bed and a second heat exchanger is located at the top of the catalyst bed, which also receives quench gas flow. The Braun adiabatic synthesis converter illustrated on page 365 of the same book utilizes downflow through the catalyst bed. The OSW ammonia converter illustrated on page 315 utilizes interbed heat transfer with axial flow through annular-shaped catalyst beds.
U.S. Pat. No. 3,918,918 discloses a catalytic reactor for processes such as ammonia synthesis which includes a two-stage, single catalyst bed and heat exchanger positioned within a single vessel. In the catalytic reactor of U.S. Pat. No. 3,918,918, the synthesis gas feed is passed through a heat exchanger and then mixed with a second feed line prior to successively passing radially outwardly through first and second stages of the catalytic bed. The combined feed gas stream is passed through the tube side of the initial heat exchanger for heating the entering feed gas prior to passing to the second stage catalytic bed.
U.S. Pat. No. 3,754,078 discloses a vessel containing an annular catalyst bed utilizing gradation of the surface of the catalyst bed exposed to flow for a more uniform distribution of gas through the bed.
U.S. Pat. No. 3,567,404 illustrates a reactor vessel which includes a heat exchanger and a series of catalytic reaction beds having entrance areas disposed parallel to the longitudinal axis of the outer and inner vessel shells for the purpose of providing reactant gas flow through consecutive catalyst beds in a direction perpendicular to the longitudinal axis of the vessel. U.S. Pat. Nos. 3,784,361; 3,964,169; 3,475,136; and 3,031,274 illustrate ammonia synthesis converters or vessels which utilize catalyst zones providing for axial gas flow therethrough.
The utilization of annular-shaped catalyst beds for ammonia synthesis is thus known in the art. See, in addition, U.S. Pat. Nos. 3,998,932 and 3,941,869 which disclose catalytic processes for the synthesis of ammonia utilizing annular-shaped catalyst beds. U.S. Pat. Nos. 3,944,394; 3,844,936; and 2,279,153 disclose the use of annular-shaped catalyst beds in other fields.